Calpain and caspase-3 inhibitors reduce infarct size and post-ischemic apoptosis in rat heart without modifying contractile recovery.

Overactivation of proteases play a key role in the development of ischemia reperfusion (IR) myocardial injury. Calpains are calcium-dependent cysteine proteases and have been implicated in post-ischemic cell death. Moreover, activation of caspases, another family of proteases, represents an important step in the apoptotic process. We investigated the effect of leupeptin and calpain inhibitor-1 (CAI-1), two calpain inhibitors and of a caspase-3 inhibitor, Ac-DEVD-CHO, on functional recovery, myocardial infarct size and apoptosis in isolated rat hearts (Langendorff technique) subjected to 30 min of global ischemia and 120 min of reperfusion. Each inhibitor was added to the perfusion medium 10 min before ischemia and during the first 30 min of reperfusion. IR was associated with mechanical dysfunction and myocardial infarction. Apoptosis induced by this sequence was demonstrated by DNA ladder and TUNEL staining. Whereas leupeptin, CAI-1 or Ac-DEVD-CHO did not modify post-ischemic function, they significantly reduced infarct size and cardiomyocyte positive TUNEL staining. Our findings suggest that calpain and caspase-3 inhibitors may protect heart from the development of cell death induced by IR; this effect could be due, at least in part, to the reduction of apoptosis. However, in our experimental conditions, these inhibitors did not afford improvement of post-ischemic myocardial function.